This is a beautiful and important painting, a beguiling example of Manet's louche modernity. I would love the Ashmolean to own it – why not? But this rhetoric about "saving" art has to stop. Unless the potential foreign owner is a wealthy maniac who bought it with the express intention of shredding the canvas and feeding it to the hounds, or a thriller writer who wants to do CSI on it to find out if Manet was Jacques le Ripper, or an agent for the Chapman brothers, the painting is not in any need of being "saved". If it did leave these shores, it would be no great loss to most of us, who have never seen it in a British gallery and had little idea it was even in the country. For all those years, it has not been a public possession but a very private one. It is only the prospect of a sale abroad that has suddenly made it news, got it shown in the media, and provoked this campaign.

It is hard to argue that a regional museum in southern England needs a world-class Manet for any reason beyond its own ambition. People living in Oxford are not that deprived of the Frenchman's genius: they can easily get to London, where they can see great works by him at the Courtauld Gallery, as well as at the National Gallery. I bet there are a few who could even manage the occasional Eurostar trip to the Musée d'Orsay in Paris.

It is almost impossible to defend art honestly. The language of politics – as George Orwell argued in a famous essay – is inherently false and deadening. When it comes to art, politics demands that every commission, every purchase, every gallery be a service to society and a national necessity. Any institution that needs public funds has to speak this language, and so ends up talking gobbledegook. A Manet must be "saved", as if it were a victim of something, and a museum's perfectly justifiable ambition has to be presented as a humble public service. The honest thing for the Ashmolean would be to say, "We really fancy this Manet, it's fantastic, we think it would look great in our collection and it would bolster our claim to be a really glamorous big-time gallery."

Art does not heal the sick, or feed the poor. It is useless. It is gratifying. It should never be spoken of in the miserable language of need, or seen as a vulnerable object of charitable concern. That is to confuse things and people. Save people. Enjoy art.